CHN, CHA, NYN, NYA, etc. make me think of early 90s computer games that had no official MLB affiliations. I've always gone with two letters when abbreviating for the Rays, Royals, Giants and Padres. My abbreviations go: NYM, PHI, WAS, MIA, ATL CHC, MIL, STL, CIN, PIT LAD, SF, SD, ARZ, COL NYY, BOS, TOR, BAL, TB CLE, CHW, DET, MIN, KC HOU, LAA, TEX, SEA, OAK